<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="https://cdn.jsdelivr.net/npm/vue@2.6.14/dist/vue.js"></script>
</head>

<body>
  <div id="el">
    <button v-on:click="clickHandler()">点击</button>
    <p>{{dog}}</p>
  </div>

  <script>
    let vm = new Vue({
      el: '#el',
      data: {
        o: 'object',
        dog: {}
      },
      methods: {
        clickHandler: function () {
          this.$set(this.dog, 'name', 'Trump')
        }
      }
    })
  </script>
</body>

</html>